Office-side line concentrator , access controller  and computer program therefor

ABSTRACT

There is provided an office-side line concentration device that accommodates a plurality of passive optical networks, including a plurality of receiving means connected to each of the plurality of passive optical networks, and interface means for controlling a transmission timing of user data from the plurality of passive optical networks so that user data received by the plurality of receiving means can be arranged closely in an uplink, thus enabling effective use of bandwidth in the uplink

RELATED APPLICATIONS

This application is the U.S. National Phase under 35 U.S.C. §371 ofInternational Application No. PCT/JP2008/070915, filed on Nov. 18, 2008,which in turn claims the benefit of Japanese Application No.2007-322212, filed on Dec. 13, 2007, the disclosures of whichApplications are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a PON (Passive Optical Network) thatprovides shared-medium communication in which a plurality of home-sidedevices share a medium to transmit data, and more specifically to anoffice-side line concentration device that accommodates a plurality ofEPONs (Ethernet (registered trademark) PONs) for providing transmissionof data in the form of Ethernet (registered trademark) frames and thatmultiplexes the data frames on an upper network (hereinafter referred toas an uplink), an access control device, and a computer programtherefor.

BACKGROUND ART

Recently, the Internet has been widely spread, and users can accessvarious information in websites around the world to obtain theinformation. In accordance therewith, devices capable of broadbandaccess such as ADSL (Asymmetric Digital Subscriber Line) and FTTH (FiberTo The Home) have also become rapidly widespread.

Related art techniques relating thereto include techniques disclosed inPatent Document 1 and Non-Patent Document 1 below. In an office-sideline concentration device disclosed in Patent Document 1, a buffermemory, a receiving unit, a transmitting unit, and a PON IF (interfaceunit) are provided for each of a plurality of PON transmission lines A,B, . . . , and Z. A control unit generates control frames so that normalframes received via the PON transmission lines A, B, . . . , and Z donot conflict, and sends the control frames to the PON transmission linesA, B, . . . , and Z.

Further, Non-Patent Document 1 specifies EPON access control protocols(MPCP (Multi-Point Control Protocol)) and OAM (Operations,Administration and Maintenance) protocols, and describes a method forregistering a new home-side device using MPCP messages, bandwidthallocation requests, transmission instructions, and the like.

Patent Document 1: Japanese Unexamined Patent Application PublicationNo. 2004-253881

Non-Patent Document 1: IEEE Std 802.3ah (registered trademark)-2004

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

FIG. 21 is a diagram illustrating an example of an access control methodin the office-side line concentration device disclosed in PatentDocument 1. In FIG. 21, a case where user data frames from PON lines 1and 2 are multiplexed and sent to an uplink is illustrated. A laser-offperiod in the PON line 1 and a laser-on period in the PON line 2 aremade to overlap to effectively use bandwidth.

In the uplink, however, an amount of unused bandwidth equivalent to thelaser-on period, synchronization period, and management-use framesending period in the PON line 2 occurs between the user data frame fromthe PON line 1 and the user data frame from the PON line 2, and thebandwidth may not necessarily be sufficiently effectively used.

Furthermore, for example, when the transfer rate of the PON line 1 andthe transfer rate of the PON line 2 are different, a larger amount ofunused bandwidth in the uplink may be produced.

The present invention has been made in order to solve the above problem,and an object thereof is to provide an office-side line concentrationdevice, an access control device, and a computer program therefor whichenable effective use of bandwidth in an uplink.

Means for Solving the Problems

According to an aspect of the present invention, there is provided anoffice-side line concentration device that accommodates a plurality ofpassive optical networks, including a plurality of receiving meansconnected to each of the plurality of passive optical networks, andinterface means for controlling a transmission timing of user data fromthe plurality of passive optical networks so that user data received bythe plurality of receiving means can be arranged closely in an uplink.

The interface means controls a transmission timing of user data from aplurality of passive optical networks so that user data received by theplurality of receiving means can be arranged closely in an uplink, thusenabling effective use of bandwidth in the uplink.

Preferably, the interface means controls the transmission timing so thata difference between a reception timing of the user data received by thereceiving means and a transmission timing to the uplink can be reduced.

The interface means controls the transmission timing so that adifference between a reception timing of the user data received by thereceiving means and a transmission timing to the uplink can be reduced,thus enabling more effective use of bandwidth in the uplink.

Further preferably, all upstream transfer rates of user data in thepassive optical networks are identical to an upstream transfer rate ofthe uplink, and the interface means transmits the user data received bythe plurality of receiving means directly to the uplink withoutaccumulating the user data in a buffer.

The interface means transmits the user data received by the plurality ofreceiving means directly to the uplink without accumulating the userdata in a buffer, thus requiring no buffers and enabling a reduction inthe cost of the apparatus.

Further preferably, the interface means controls the reception timing sothat a burst signal of a first passive optical network and a burstsignal of a second passive optical network are made to overlap and sothat an overlapped time can become at least a portion of a time obtainedby removing a time corresponding to a user data frame period and alaser-off period from a burst length of the second passive opticalnetwork.

The interface means controls the reception timing so that a burst signalof a first passive optical network and a burst signal of a secondpassive optical network are made to overlap and so that an overlappedtime can become at least a portion of a time obtained by removing a timecorresponding to a user data frame period and a laser-off period from aburst length of the second passive optical network, thus enablingsuccessive transmission of user data frames in the uplink.

Further preferably, the plurality of passive optical networks include apassive optical network including a home-side device having a lowerupstream transfer rate than an upstream transfer rate of the uplink, andthe interface means controls the reception timing so that, when userdata from the home-side device having a lower upstream transfer ratethan that of the uplink is up-converted and transmitted to the uplink,the end of the user data from the home-side device having a lowerupstream transfer rate can exist before the end of the user dataup-converted and transmitted to the uplink.

The plurality of passive optical networks include a passive opticalnetwork including a home-side device having a lower upstream transferrate than an upstream transfer rate of the uplink, and the interfacemeans controls the reception timing so that, when user data from thehome-side device having a lower upstream transfer rate than that of theuplink is up-converted and transmitted to the uplink, the end of theuser data from the home-side device having a lower upstream transferrate can exist before the end of the user data up-converted andtransmitted to the uplink, thus enabling more effective use of bandwidthof the uplink.

Further preferably, the interface means controls the reception timing sothat a burst signal of a first passive optical network and a burstsignal of a second passive optical network are made to overlap and sothat an overlapped time can become at least a portion of a time obtainedby removing a time required to transmit a user data frame at an uplinkspeed and a time corresponding to a laser-off period from a burst lengthof the second passive optical network.

The interface means controls the reception timing so that a burst signalof a first passive optical network and a burst signal of a secondpassive optical network are made to overlap and so that an overlappedtime can become at least a portion of a time obtained by removing a timerequired to transmit a user data frame at an uplink speed and a timecorresponding to a laser-off period from a burst length of the secondpassive optical network, thus enabling successive transmission of userdata frames in the uplink.

According to another aspect of the present invention, there is providedan access control device that controls a reception timing of user datafrom a plurality of passive optical networks, including means forcontrolling a transmission timing of user data from the plurality ofpassive optical networks so that user data received by the plurality ofpassive optical networks can be arranged closely in an uplink, and meansfor instructing transmission of a grant including the transmissiontiming to home-side devices connected to the passive optical networks.

According to still another aspect of the present invention, there isprovided a computer program for causing a computer to execute control ofa reception timing of user data from a plurality of passive opticalnetworks, causing the computer to execute a step of controlling atransmission timing of user data from the plurality of passive opticalnetworks so that user data received by the plurality of passive opticalnetworks can be arranged closely in an uplink, and a step of instructingtransmission of a grant including the transmission timing to home-sidedevices connected to the passive optical networks.

Advantages

According to an aspect of the present invention, interface meanscontrols a transmission timing of user data from a plurality of passiveoptical networks so that user data received by the plurality ofreceiving means can be arranged closely in an uplink, thus enablingeffective use of bandwidth in the uplink.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for describing an example of an access controlmethod in an office-side line concentration device according to a firstembodiment of the present invention.

FIG. 2 is a block diagram illustrating an example configuration of theoffice-side line concentration device according to the first embodimentof the present invention.

FIG. 3 is a block diagram illustrating an example configuration of a4-to-1 MUX 31.

FIG. 4 is a diagram illustrating an example configuration of an accesscontrol unit 11 when implemented in software.

FIG. 5 is a flowchart for describing a procedure of an initializationprocess of the access control unit 11.

FIG. 6 is a flowchart for describing a procedure of an interrupt processroutine.

FIG. 7 is a flowchart for describing a procedure of a discovery process.

FIG. 8 is a flowchart for describing a procedure of a timeout process.

FIG. 9 is a flowchart for describing a procedure of a TOCn process.

FIG. 10 is a flowchart for describing a procedure of a message receivingprocess.

FIG. 11 is a flowchart for describing a procedure of a registrationrequest process.

FIG. 12 is a flowchart for describing a procedure of a registrationconfirmation process.

FIG. 13 is a flowchart for describing a procedure of a de-registrationprocess.

FIG. 14 is a flowchart for describing a procedure of a report receivingprocess.

FIG. 15 is a flowchart for describing a procedure of an RTT updateprocess.

FIG. 16 is a flowchart for describing a procedure of a bandwidthallocation process.

FIG. 17 is a block diagram illustrating an example configuration of aPON communication unit 21.

FIG. 18 is a diagram for describing an example of an access controlmethod in an office-side line concentration device according to a secondembodiment of the present invention.

FIG. 19 is a diagram illustrating an example of connection of a lineconcentrator 100 according to an embodiment of the present invention.

FIG. 20 is a block diagram illustrating an example configuration of aPON communication unit 21′ according to the second embodiment of thepresent invention.

FIG. 21 is a diagram illustrating an example of an access control methodin an office-side line concentration device disclosed in Patent Document1.

REFERENCE NUMERALS

-   -   1 uplink IF unit,    -   2 PON IF unit,    -   11 access control unit,    -   12 uplink transmitting/receiving unit,    -   13 DEMUX,    -   14 line concentration unit,    -   21 PON communication unit,    -   22 PON transmitting/receiving unit,    -   31 4-to-1 MUX,    -   41 input unit,    -   42, 62, 71, 72 FIFO,    -   43 MUX control unit,    -   44 multiplexer,    -   45 output unit,    -   51 CPU,    -   52 ROM,    -   53 RAM,    -   54 shared memory,    -   55 input/output unit,    -   56 clock timer,    -   61 input unit,    -   63 transmission processing unit,    -   64 reception processing unit,    -   65 management frame processing unit,    -   66 MPCP frame processing unit,    -   68 output unit,    -   100 office-side line concentration device, and    -   101 home-side device.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described hereinafter withreference to the drawings. In the following figures, the same orcorresponding portions will not be described redundantly.

First Embodiment

FIG. 1 is a diagram for describing an example of an access controlmethod in an office-side line concentration device according to a firstembodiment of the present invention. In the present embodiment, accesscontrol is performed so that a user data frame sending period of a PONline 1 is made to overlap a laser-on period, synchronization period,report frame sending period, and management-use frame sending period ofa PON line 2. Thus, user data frames from the PON line 1 and user dataframes from the PON line 2 are successively sent to an uplink. The termsuccessively (or closely), as used herein, refers to an interval atwhich user data frames are sent to the uplink, which is greater than orequal to a minimum IFG (Inter Frame Gap) and less than a maximumoverhead time. The maximum overhead time is a time corresponding to thelaser-on period, the synchronization period, and the report frame andmanagement-use frame sending periods.

In FIG. 1, a report frame, a management-use frame, and user frames aretransmitted in this order from a home-side device after thesynchronization period. However, the order of the frames is arbitrary.Access control may be performed so that an overlap of a time obtained bysubtracting the time corresponding to the user data frames periodincluding the IFG and the preamble and the laser-off period from theburst length (time) of the PON line 2 can be used. In this case, userdata frames may overlap between consecutive bursts. However, thecollision of the user data frames can be avoided because they are placedin the uplink after being subjected to delay adjustment using FIFOs(First In First Outs) described below. Further, the overlap time may beset to that in the above example at maximum or may be set to a lessvalue.

FIG. 2 is a block diagram illustrating an example configuration of anoffice-side line concentration device according to the first embodimentof the present invention. This office-side line concentration deviceincludes an uplink IF (Interface) unit 1 and N PON IF units 2. In theconfiguration illustrated in FIG. 2, N=16, and 16 PON lines i (i=1 to16) are concentrated. However, the number of PON lines is not limited tothis.

The PON lines may not necessarily be passive. In general, splitting isperformed using optical couplers but may be performed using activeoptical switches instead. Here, a PON line mean a line that accommodatesa plurality of home-side devices using MPCP.

A description will be given of a case where an uplink is implementedusing a 10 GE (10 gigabit Ethernet (registered trademark)) uplink andwhere a PON line is implemented using a 10 G-EPON (10 gigabit Ethernet(registered trademark) PON) line. However, an uplink may be implementedusing a GE (gigabit Ethernet (registered trademark)) uplink and a PONline may be implemented using a GE-PON (gigabit Ethernet (registeredtrademark) PON) line.

The uplink IF unit 1 includes an access control unit 11 that performsupstream access control for an uplink and each of the PON lines, anuplink transmitting/receiving unit 12 that transmits and receives framesto and from the uplink, a DEMUX 13 that outputs a downstream signalreceived by the uplink transmitting/receiving unit 12 to the individualPON IF units 2, and a line concentration unit 14 that multiplexesupstream signals from the individual PON IF units 2 and that outputs aresulting signal to the uplink transmitting/receiving unit 12.

Further, each of the PON IF units 2 includes a PONtransmitting/receiving unit 22 that transmits and receives signals toand from the corresponding one of the PON lines, and a PON communicationunit 21 that terminates data links to home-side devices connected to thePON line and that relays main signals directed to the uplink.

The DEMUX 13 outputs a downstream signal received by the uplinktransmitting/receiving unit 12 to the individual PON IF units 2. TheDEMUX 13 may send a downstream signal delivered from the uplinktransmitting/receiving unit 12 directly to the individual PON IF units2, or may analyze the content of downstream frames to identify thetransmission destinations of the frames and selectively send them tocorresponding ones of the PON IF units 2. The identification may beperformed using VLAN (Virtual Local Area Network) tags, or using MAC(Media Access Control) addresses.

The line concentration unit 14 is configured using a plurality of 4-to-1MUXes 31 each of which multiplexes four lines, and the plurality of4-to-1 MUXes 31 are multi-connected to implement a desired number ofmultiplexes N. In the present embodiment, five 4-to-1 MUXes 31 aremulti-connected to implement a 16-to-1 MUX.

FIG. 3 is a block diagram illustrating an example configuration of a4-to-1 MUX 31. The 4-to-1 MUX 31 includes four input units 41 each ofwhich is connected to the corresponding one of the PON IF units 2, fourFIFOs (First In First Outs) 42 individually connected to the input units41, a MUX control unit 43 that receives a notification of the amount ofaccumulated frames from each of the FIFOs 42 and that controls theoutput of frames accumulated in the FIFOs 42, a multiplexer 44, and anoutput unit 45 that outputs frames from the multiplexer 44 to thesubsequent 4-to-1 MUX 31 or the uplink transmitting/receiving unit 12.

The input units 41 convert high-speed serial signals from the PON IFunits 2 into low-speed parallel internal signals which are accumulatedin the FIFOs 42. The internal signals can be 64-bit 156.25-Mbps signals.The FIFOs 42 notify the MUX control unit 43 of the accumulation state offrames.

The MUX control unit 43, which monitors the status of the FIFOs 42,exclusively extracts frames from the FIFOs 42 in which the frames areaccumulated, and outputs the frames to the output unit 45 whilecontrolling the multiplexer 44.

The output unit 45 converts the frames received from the multiplexer 44into high-speed serial signals, for example, XAUI (10 Gbps AttachmentUnit Interface) signals, and outputs the resulting signals.

As described below, the access control unit 11 performs access controlso that upstream signals in PON lines can be output directly to theuplink, and therefore the capacity of FIFOs may be small. That is, theseFIFOs are designed to avoid temporary collision due to the deviationdependent upon accuracy, the difference in arrangement of user dataframes in a burst, or the like or to absorb slight shift between theinput and output clock frequencies. If the access control unit 11provides sufficient allocation intervals between the PON lines, each ofthe 4-to-1 MUXes 31 can be configured such that the FIFOs 42 and the MUXcontrol unit 43 are removed so that frames can be forwarded directlyfrom the input units 41 to the multiplexer 44. In this case, themultiplexer 44 may be controlled by the input units 41 or may bedesigned to simply perform an OR operation (to output a logic 0 signalduring a period during which no data is output).

The PON communication units 21 are connected to the access control unit11 via control lines. MPCP frames are transmitted and received by thePON communication units 21 while MPCP messages pass through the PONcommunication units 21 and terminate at the access control unit 11. Inthis case, the PON communication units 21 may add a timestamp at thetime of PON reception or overwrite a timestamp at the time of PONtransmission. This prevents a dependence of the RTT (Round Trip Time) ortimestamp drift upon an internal processing delay of the access controlunit 11, and increases accuracy. It is assumed that the access controlunit 11 and each of the PON communication units 21 have a common clock.

FIG. 4 is a diagram illustrating an example configuration of the accesscontrol unit 11 when implemented in software. It is to be understoodthat the access control unit 11 may also be implemented by hardware.

The access control unit 11 includes a CPU (Central Processing Unit) 51,a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, a sharedmemory 54, an input/output unit 55, and a clock timer 56.

The CPU 51 executes an access control program stored in the ROM 52,thereby implementing the functions of the access control unit 11.Further, the RAM 53 holds various information used for access control.The details of the various information will be described below.

The input/output unit 55 is connected to the PON IF units 2, andcontrols the input and output of messages. Upon receipt of messagesignals received by the PON IF units 2, the input/output unit 55converts the message signals into the internal format, and adds theresults to an input message queue (Qin) of the shared RAM 54. In thiscase, when the Qin is changed from an empty state to a non-empty state,the input/output unit 55 sends an interrupt to the CPU 51.

Further, in accordance with an instruction from the CPU 51, theinput/output unit 55 outputs messages accumulated in an output messagequeue (Qeg) in the shared RAM 54 to the PON IF units 2.

The clock timer 56 has a clock function for measuring the current time(ctime), and a counter function for counting predetermined times. Thevalue of the ctime of the clock timer 56 is referred to by the CPU 51.

In a case where the clock timer 56 functions as a discovery timer (TD)and a logical link timer (TLij: i=1, 2, . . . , N: j E {the LLIDs(Logical Link IDs) of the PON IFs i}) described below, when a countvalue reaches a value set by the CPU 51, the clock timer 56 sends aninterrupt to the CPU 51 and notifies it of a count-out.

FIGS. 5 to 15 are flowcharts for describing a process procedure of theaccess control unit 11. The various information held in the RAM 53 willnow be described.

A final allocation time (TEi: i=1, 2, . . . , N) is based on an overlapof the laser-off period (Toff) and the laser-on period (Ton), and is atime obtained by subtracting the amount of Toff from the final time ofthe grant period. In FIG. 1, for example, the end time of the user dataframe in the PON line 1 (laser-off start time) is a final allocationtime. This final allocation time is held in the RAM 53 for each of the NPON IFs.

In a case where the grant period does not include a minimum IFG(interframe gap) after the last frame, the minimum IFG is added to thefinal allocation time. Note that no overlap may be assumed and that Toffmay not be subtracted.

An overall final allocation time (TEz) is only one time held in the RAM53, and is basically the final allocation time of the last allocated PONIF k. However, there may also be an exception. This exception will bedescribed later.

A discovery order list (dLST) is designed such that the order of PON IFsto be subjected to a discovery process is held in list form, and is setto, for example, 1→2→ . . . →N→1 or the like.

Logical link information (LLTij: i=1, 2, . . . , N: j ε {the LLIDs ofthe PON IFs i}) is information held in the RAM 53 in table form for eachlogical link, and includes a logical link status (LLstat), a reportstatus (RPstat), a management-frame-use report information (RPm),user-data-use report information (RPu), and RTT (Round Trip Time)information. The report information may reflect the latest report forsimplicity, or may be in queue form.

The logical link status (LLstat) is information indicating the status ofa logical link, and has the following states: unregistered,registration-in-progress, and registered.

The report status (RPstat) is information indicating whether the reportof the logical link is valid or invalid.

The management-use frame report information (RPm) is informationindicating the time required to send reported management-use frames.

The user-data-use report information (RPu) is information indicating thetime required to send reported user data frames.

The access control unit 11 is given the allocation order of the PON IFsand the allocation order of the logical links in the PON IFs. Theallocation order may be determined using a simple round robin method orany other method such as a weighted round robin method, a hierarchicalround robin method for differentiating allocation cycles, or skippingthe allocation of logical links that are excessively allocated based onbandwidth calculation.

The allocation order is systematized in general scheduling techniques,and the present invention does not depend upon a specific schedulingtechnique. However, non-consecutive allocations to the same PON IF canprovide improvement of the advantageous effects of the presentinvention.

Further, the present invention bears no relation to the timing ofallocation. The allocation may be performed each time a report frame isreceived or may be performed after report frames have been intensivelycollected.

FIG. 5 is a flowchart for describing the procedure of the initializationprocess of the access control unit 11. First, the input message queueQin and the output message queue Qeg are brought into an emptycondition, all the pieces of logical link information LLTij (i=1, 2, . .. , N: j ε {the LLIDs of the PON IFs i}) are set to NULL, and all thefinal allocation times TEi are set to the current time ctime, theoverall final allocation time TEz is set to ctime, and the discoveryorder list dLST is set to 1→2→ . . . →N→1 (S11).

Next, the discovery timer TD is set to the value obtained by dividing adiscovery cycle discovery_interval by N (S12). TD represents an intervalat which the discovery process is performed in sequence on the N PONlines, and the discovery process is performed on the subsequent PON lineeach time TD has elapsed.

Next, the process waits for an interrupt to occur (S13). When aninterrupt occurs (S13, Yes), the process proceeds to an interruptprocess routine (S14).

FIG. 6 is a flowchart for describing the procedure of the interruptprocess routine. First, the routine branches depending on the type ofthe interrupt (S21). When the interrupt indicates that the Qin is notempty (S21, non-empty Qin), the routine proceeds to a message receivingprocess (S22). When the interrupt indicates a count up of TD (S21, TDexpired), the routine proceeds to a discovery process (S23). Further,when the interrupt indicates a count up of TLij (S21, TLij expired), theroutine proceeds to a timeout process (S24).

It is assumed that an interrupt indicating that the Qin is not empty isassigned the highest priority and that interrupts are assigned lowerpriorities in decreasing order of TD expired and TLij expired.

FIG. 7 is a flowchart for describing the procedure of the discoveryprocess. First, assuming that the top of the dLST is represented by k, adiscovery gate message for the PON IF k is configured and is placed inthe Qeg. In this case, the start time is based on the later one of theTEk and the current time (S31).

Next, the end of the discovery period is set as the new TEk, and thedLST moves to the subsequent PON IF unit (S32). Then, the discoverytimer TD is set (S33), and the process ends.

FIG. 8 is a flowchart for describing the procedure of the timeoutprocess. First, it is determined whether or not the LLstat in the LLTijindicates registration-in-progress (S41). When it does not indicateregistration-in-progress (S41, No), timeout information is recorded inthe LLTij. Then, previous timeout information is referred to, and thenumber of timeouts TOCij within a predetermined period of time isdetermined. Here, the maximum allowable value is represented by TOCmax(S42).

Next, TOCij is compared with TOCmax. When TOCil is less than or equal toTOCmax (S43, No), the process proceeds to a TOCn process illustrated inFIG. 9. When TOCij is greater than TOCmax (S43, Yes), a de-registrationprocess is performed (S44).

When, in step S41, the LLstat in the LLTij indicatesregistration-in-progress (S41, Yes), the de-registration process isperformed (S44).

FIG. 9 is a flowchart for describing the procedure of the TOCn process.First, a gate message for the LLIDj of the PON IF i is configured and isplaced in the Qeg. In this case, a forced-report flag is set to make aforced-report instruction. Further, the start time is based on the TEior the current time, and the grant length is set to an amount by whichonly the report frame can be transmitted (S51).

Then, the laser-off start of the grant is set as the new TEi, and a timeestimated with a certain amount of deviation time therefrom is set inthe timer TLij (S52). Then, the process ends.

FIG. 10 is a flowchart for describing the procedure of the messagereceiving process. A timestamp recorded on a message using a home-sidedevice is represented by T1, and a timestamp added by the PONcommunication unit 21 when the message is received is represented by T2.

First, the top message is extracted from the Qin (S61). When the type ofthe message is registration request (S62, registration request), aregistration request process is performed (S63). When the type of themessage is registration confirmation (S62, registration confirmation), aregistration confirmation process is performed (S64).

When the type of the message is de-registration request (S62,de-registration request), a de-registration process is performed (S65).When the type of the message is report (S62, report), a report receivingprocess is performed (S66), and a bandwidth allocation process isperformed (S67).

When the processing of steps S63 to S65 or the processing of S67 iscompleted, it is determined whether or not the Qin is empty (S68). Whenthe Qin is not empty (S68, No), the process returns to step S61, and theprocessing subsequent thereto is performed. When the Qin is empty (S68,Yes), the process ends.

FIG. 11 is a flowchart for describing the procedure of the registrationrequest process. It is assumed that this registration request is arequest issued from a home-side device being connected to PON IF i, forwhich the MAC address is m.

First, a new LLID is assigned to the present PON IF from which theregistration request has been issued, and is represented by LLIDj. Then,the LLstat in the LLTij is set to registration-in-progress, RPstat isset to NULL, and the RTT is set to (T2−T1) (S71).

Next, a registration message for the PON IF i is configured and isplaced in the Qeg. In this case, the DA (Destination Address) is set tom, and the LLID is set to j (S72). Note that this LLID is written in theregistration message and is reported to the home-side device and thatthe LLID written in the header portion of the frame is a broadcast LLID.

Next, a gate message for the PON IF i, LLIDj is configured and is placedin the Qeg. In this case, the start time is based on the TEi or thecurrent time. Further, the grant length is set to an amount by whichonly the registration confirmation frame can be transmitted (S73).

Finally, the laser-off start of the grant is set as the new TEi, and atime estimated with a certain amount of deviation time therefrom is setin the timer TLij (S74). Then, the process ends.

FIG. 12 is a flowchart for describing the procedure of the registrationconfirmation process. First, RTT is recalculated, and the RTT updateprocess of the corresponding logical link is performed. In this case,when the drift exceeds a specified value (S81, NG), the process ends.

When the drift is equal to or below the specified value (S81, OK), theLLstat in the LLTij is set to registered, and a gate message for the PONIF i, LLIDj is configured and is placed in the Qeg. In this case, aforced-report flag is set to make a forced-report instruction. Further,the start time is based on the TEi or the current time. Preferably, theprevious reservation order is referred to and the same PON IF is placedat positions that are spaced apart. Then, the grant length is set to anamount by which only the report frame can be transmitted (S82).

Next, the laser-off start of the grant is set as the new TEi, and a timeestimated with a certain amount of deviation time therefrom is set inthe timer TLij (S83). Then, the process ends.

FIG. 13 is a flowchart for describing the procedure of thede-registration process. It is assumed that the PON IF i, LLIDj is to bede-registered. First, a de-registration message for the PON IF i, LLIDjis configured and is placed in the Qeg (S91). Then, the LLstat in theLLTij is set to NULL (S92), and the process ends.

FIG. 14 is a flowchart for describing the procedure of the reportreceiving process. It is assumed that a report from the PON IF i, LLIDjis to be received. First, RTT is recalculated, and the RTT updateprocess of the corresponding logical link is performed. In this case,when the drift exceeds a specified value (S101, NG), the process ends.

When the drift is equal to or below the specified value (S101, OK), thenthe RPstat in the LLTij is set valid, the RPm is updated to amanagement-frame-use report queue queue0_report, and the RPu is updatedto the sum of user-frame-use report queues queueK_report (S102). Then,the process ends.

FIG. 15 is a flowchart for describing the procedure of the RTT updateprocess. First, the new RTT is updated to (T2−T1) (S111), and it isdetermined whether or not the difference between the new RTT and theoriginal RTT is greater than a maximum drift value DRIFTmax (S112).

When the difference between the new RTT and the original RTT is lessthan or equal to the DRIFTmax (S112, No), the new RTT is set in the RTTin the LLTij (S113), and it is determined that the RTT update processhas been successfully performed (OK). When the difference between thenew RTT and the original RTT is greater than the DRIFTmax (S112, Yes),the de-registration process is performed (S114), and it is determinedthat the RTT process has failed (NG).

FIG. 16 is a flowchart for describing the procedure of the bandwidthallocation process. It is assumed that bandwidth is to be allocated tothe PON IF i, LLIDj. First, the sum of the time RPm required to send themanagement-use frame in the LLTij and the time REPORT_length required tosend the report frame is represented by ML, that the time RPu requiredto send the user data frame in the LLTij is represented by UL, and thatthe overhead time (laser-on period Ton+synchronization period SyncTime)at the beginning of the burst is represented by OVL. Then, the smallervalue of the sum of ML, UL, OVL, and Toff and the upper limit valueGLmax of the grant length is represented by grant length GL.

The time obtained by subtracting OVL and ML from the overall finalallocation time TEz is represented by TSz. The sum of the finalallocation time TEi of the PON IF i and the burst gap time burst gap isrepresented by TSi. Further, the sum of the current time ctime, the RTT,and the processing time proc_time of the home-side device is representedby TSc. Then, the latest time of TSz, TSi, and TSc is represented by TS(S121).

Next, the time obtained by subtracting the current time ctime from TS iscompared with a system constant TooFar that is adapted to prevent theexcessive precedence of the grant (S122). When the value given byTS®-ctime is not smaller than the TooFar (S122, No), the process waitsor sleeps until the value given by TS−ctime is smaller than the TooFar(S123). Then, the process returns to step S121, and the processingsubsequent thereto is repeated.

When the value given by TS−ctime is smaller than the TooFar (S122, Yes),a gate message for the PON IF i, LLIDj is configured and is placed inthe Qeg. In this case, a forced-report flag is set to make aforced-report instruction. Further, the start time is set to (TS−WIT),and the grant length is set to GL (S124). Then, the TEi is set to(TS+GL−Toff) (S125).

Next, it is determined whether or not the UL is greater than 0 (S126).When the UL is 0 (S126, No), the process proceeds to step S128 withoutupdating the TEz. When the UL is greater than 0 (S126, Yes), the TEz isset to the TEi (S127).

Finally, the timer TLij is set to a time estimated with a certain amountof deviation time from the TEi (S128), and the process ends.

Note that simplicity may be preferential and that the ML may be includedin the UL. Furthermore, the grant start time may be deliberately shiftedfrom the best one.

At the end of the process, the report status of the correspondinglogical link in the LLTij is invalidated. However, in a case where thereport information is in queue form and a next entry exists, the reportqueue is updated with the report status kept valid.

FIG. 17 is a block diagram illustrating an example configuration of thePON communication unit 21. The PON communication unit 21 includes aninput unit 61 that receives a signal (internal format signal) from theDEMUX 13, a FIFO 1 (62) that accumulates signals input to the input unit61, a transmission processing unit 63 that extracts the data accumulatedin the FIFO 1 (62) and that converts the signal format and then outputsthe resulting data to the PON transmitting/receiving unit 22, areception processing unit 64 that determines the type of a frame inputfrom the PON transmitting/receiving unit 22 and that selectively outputsthe frame, a management frame processing unit 65 that receives amanagement frame from the reception processing unit 64 and thatprocesses the management frame, an MPCP frame processing unit 66 thatreceives an MPCP frame from the reception processing unit 64 and thatprocesses the MPCP frame, and an output unit 68 that receives a userdata frame from the reception processing unit 64 and that converts thesignal format and then outputs the user data frame to the lineconcentration unit 14. The PON communication unit 21 is generallyimplemented by one or a plurality of LSIs.

In a case where data has been accumulated in the FIFO 1 (62), thetransmission processing unit 63 extracts the data, converts the signalformat, and outputs the resulting data to the PON transmitting/receivingunit 22. However, when the management frame processing unit 65 or theMPCP frame processing unit 66 has a frame to be transmitted, thetransmission processing unit 63 prioritizes the output of this frame. Inthis case, the highest priority is assigned to the MPCP frame. Further,the timestamp may be overwritten as required.

The management frame processing unit 65 processes a management frame forOAM, authentication, encryption setting, and the like. The presentinvention bears no relation to the content of the process itself whichwill not be described in detail. The management frame processing unit 65configures a management frame that is required as a result of thisprocess or voluntarily, and requests the transmission processing unit 63to transmit it. In addition, as a result of the process, in a statewhere a certain logical link cannot be maintained, the management frameprocessing unit 65 instructs the MPCP frame processing unit 66 tode-register this logical link.

The MPCP frame processing unit 66 performs a process in accordance withthe type of the MPCP frame input from the reception processing unit 64.When the MPCP frame is a registration request frame, the MPCP frameprocessing unit 66 performs authentication. When the authenticationresult is correct, the MPCP frame processing unit 66 transfers aregistration request message to the access control unit 11. Note thatthe MPCP frame processing unit 66 may transfer the message to the accesscontrol unit 11 without performing authentication. Alternatively, first,the message may be transferred to and registered in the access controlunit 11 and then, the management frame processing unit 65 may performauthentication using another protocol.

When the MPCP frame is a de-registration request frame or a registrationconfirmation frame, messages for them are transferred to the accesscontrol unit 11. In this case, a timestamp may be added.

When the MPCP frame is a report frame, the MPCP frame processing unit 66checks the timestamp drift, and, when violation occurs, transfers ade-registration message to the access control unit 11. This check may beperformed by the access control unit 11. When no violation occurs, thereport message is transferred to the access control unit 11.

The MPCP frame processing unit 66 may add a timestamp when transferringthe above messages to the access control unit 11.

The MPCP frame processing unit 66 monitors the intervals of reportframes for each logical link, and determines connectivity. Then, when itis determined that the logical link has been disconnected or when ade-registration instruction is received from the management frameprocessing unit 65, the MPCP frame processing unit 66 transfers ade-registration message of the logical link to the access control unit11. This process may be performed by the access control unit 11.

The PON communication unit 21 may also include a local access controlunit (not illustrated). This local access control unit is designed tosolely perform upstream access control of a PON line, and an accesscontrol method therefor follows a related art technique. The PONcommunication unit 21 and the MPCP frame processing unit 66 can performswitching as to whether MPCP messages are to be exchanged to theoutside, for example, the access control unit 11 of the uplink IF unit1, or to the local access control unit depending on the setting.

As described above, the office-side line concentration device accordingto the present embodiment is configured such that the access controlunit 11 performs individual PON bandwidth allocations so that user dataframes from PON lines can be consecutively transmitted in an uplink,thus enabling effective use of bandwidth in the uplink.

Second Embodiment

FIG. 18 is a diagram for describing an example of an access controlmethod in an office-side line concentration device according to a secondembodiment of the present invention. In FIG. 18, a case where anupstream burst signal in a PON line 1 has a transfer rate of 10 Gbps andwhere an upstream burst signal in a PON line 2 has a transfer rate of 1Gbps is illustrated. In the present embodiment, access control isperformed so that a user data frame sending period of the PON line 1 anda user data frame sending period of the PON line 2 can be made tooverlap, thus facilitating more effective use of bandwidth in an uplink.

Since the transfer rate of the PON line 2 is lower than that of the PONline 1, a user data frame stream in the PON line 2 is up-converted tothat of the uplink speed so that the user data frames can be seamlesslyarranged in the uplink.

FIG. 19 is a diagram illustrating an example of connection of anoffice-side line concentration device 100 according to an embodiment ofthe present invention. As illustrated in FIG. 19( a), this systemincludes the office-side line concentration device 100, a home-sidedevice A 101-1 having a transfer rate α, a home-side device B 101-2having a transfer rate β, and a plurality of optical couplers 102. Thetransfer rate α is different from the transfer rate β.

As illustrated in FIG. 19( b), upstream optical signals (wavelength ◯),a downstream optical signal (wavelength C) having the transfer rate α,and a downstream optical signal (wavelength L) having the transfer rate13 are wavelength-multiplexed, and independent signal transmissions on asingle PON line are possible. On the other hand, the wavelength of theupstream optical signal having the transfer rate α and the wavelength ofthe upstream optical signal having the transfer rate p overlap. Thus, asillustrated in FIG. 19( c), time-division multiplexing is performed sothat the respective optical burst signals do not collide to provideindependent signal transmissions on a single PON line.

For example, the home-side device A 101-1 is a GE-PON device, thehome-side device B 101-2 is a 10 G-EPON device, the transfer rate α is 1Gbps, and the transfer rate (3 is 10 Gbps. These transfer rates aregeneric, and the actual transfer rates slightly change depending on thecoding scheme or before or after the coding process. When the actualeffective data rate is reduced due to the use of an error correctingcode in a PON line, the effective data rate may be considered as therate of the PON line.

Furthermore, in the present embodiment, it is assumed that thewavelength ◯ is 1260 to 1360 nm, the wavelength C is 1480 to 1500 nm,the wavelength L is 1574 to 1580 nm, and α<β.

FIG. 20 is a block diagram illustrating an example configuration of aPON communication unit 21′ according to the second embodiment of thepresent invention. The difference from the PON communication unit 21according to the first embodiment illustrated in FIG. 17 is only that aFIFO 3 (71) and a FIFO 4 (72) in which user data frames having differentrates are accumulated are added and that the functionality of a PONtransmitting/receiving unit, an input unit, a transmission processingunit, a reception processing unit, and an output unit differs.Therefore, the overlapping configurations and functions will not bedescribed in detail redundantly.

A PON transmitting/receiving unit 22′ is capable of simultaneouslytransmitting an optical signal having the wavelength C and the rate αand an optical signal having the wavelength L and the rate β. The PONtransmitting/receiving unit 22′ receives a signal having the rate α anda signal having the rate β from a transmission processing unit 63′,converts them into an optical signal having the wavelength C and therate α and an optical signal having the wavelength L and the rate β, andoutputs resulting signals to the PON line.

The PON transmitting/receiving unit 22′ is also capable of receiving adual-rate optical burst signal having the wavelength ◯. The PONtransmitting/receiving unit 22′ converts an optical signal received fromthe PON line into an electrical signal, and outputs the resulting signalto a reception processing unit 64′.

In FIG. 20, a synchronization process in accordance with the rates α andβ is performed inside the PON transmitting/receiving unit 22′, andresulting signals are output to the reception processing unit 64′ asdifferent-rate electrical signals. The synchronization process of thesesignals may be performed by the reception processing unit 64′. Thedifference in rate may be automatically recognized from the receivedsignals, or a rate of reception may be determined in advance on thebasis of information indicating a grant of transmission of the abovebursts.

Input and output signals from and to the DEMUX 13 and the lineconcentration unit 14 of the uplink IF unit 1 have a single ratecorresponding to the rate of the uplink, which is, for example, 10 Gbpsfor 10 gigabit Ethernet (registered trademark). Here, it is assumed thatthe rate is equal to β.

Upon receipt of a signal from the DEMUX 13 of the uplink IF unit 1, aninput unit 61′ determines a logical link and the rate thereof, andoutputs the signal to an FIFO corresponding to the rate. This outputsignal is converted into the internal signal format according to therate.

In a case where data has been accumulated in the FIFO 1 (62) or the FIFO3 (71), a transmission processing unit 63′ individually extracts thedata, converts the signal format, and thereafter transfers the result tothe PON transmitting/receiving unit 22′. When the MPCP frame processingunit 66 or the management frame processing unit 65 has a frame to betransmitted, such a frame is prioritized. A rate is determined using thedestination logical link of the frame, and the frame is inserted in asignal having the rate. When data flows in this signal, the frame isinserted in a frame interval.

The reception processing unit 64′ determines the type of a frame havingeach rate from the PON transmitting/receiving unit 22′, and, when it isa user data frame having the rate α, accumulates the frame in the FIFO 4(72). The reception processing unit 64′ may filter an undesired frame byreceiving time or LLID.

In addition to receiving a user data frame from the reception processingunit 64′, an output unit 68′ extracts data from the FIFO 4 (72),converts the signal format, and then outputs the resulting data to theline concentration unit 14 of the uplink IF unit 1. The timing at whichdata is started to be extracted from the FIFO 4 (72) is specified by theMPCP frame processing unit 66.

The process of the access control unit 11, which is different from thatin the first embodiment, will be described hereinafter. In the presentembodiment, it is assumed that the grant length represents time.Specifically, when the same grant length is given to 1 G and 10 Glogical links, the 10 G logical link is capable of transmittinginformation that is ten times that in the 1 G logical link.

A discovery gate is sent on a rate-by-rate basis. Therefore, the signalrates of registration requests received during the discovery period arereserved, and single rates are available. Further, the rate type isadded to logical link information and, when a registration request isreceived, the corresponding rate is recorded in the rate type. This isbased on the assumption that an uplink has a rate β and that a logicallink having the same rate (β) and a logical link having a lower rate(represented by α) exist.

When the rate type of a logical link (represented by L) of a PON IF k tobe allocated next is α, the calculation of TSz is performed using thefollowing method: Since the grant length is the time unit, the grantlength is calculated in a manner similar to that in the firstembodiment. The time required when an amount of data transmitted at therate a during the UL time is transmitted at the rate β is represented byULB. The time obtained by adding ULB to TEz is represented by TEzn. TEznis set as the laser-off start, and the time obtained by subtractingtherefrom the grant length and the burst overhead time (Ton+SyncTime) isrepresented by TSz.

When grant information is sent to the PON IF unit 2, the rate type andthe output start-enabled time TUS are added. It is assumed that TUS isobtained by subtracting ULB from the new overall final allocation time.TUS is reported to the output unit 68′ of the PON communication unit21′, and the timing at which data is extracted from the FIFO 4 (72) isspecified. The reason is to prevent FIFO underrun from occurring on thereadout side because of low write speed to the FIFO 4 (72).

In FIG. 20, signals are split for every rate in the upstream directionof the PON communication unit. However, upstream signals in a PON lineare multiplexed in the manner as illustrated in FIG. 19, and cantherefore be integrated along a path extending through a single FIFO. Inthis case, the reception processing unit 64′ increases or decreases thewrite speed to the FIFO in accordance with the rate of the receivedsignal.

When α>β, the calculation of TSz and the update of the overall finalallocation time are as follows: Since the grant length is the time unit,the grant length is calculated in a manner similar to that in the firstembodiment. The times required when amounts of data transmitted at therate a during the ML time and the UL time are transmitted at the rate βare represented by MLB and ULB, respectively. The time obtained bysubtracting OVL and MLB from the overall final allocation time TEz isrepresented by TSz.

When a selected start time is represented by TS, the time obtained byadding OVL, MLB, and ULB to TS is represented by TE. The new overallfinal allocation time is set to TE when this allocation meets UL>0. WhenUL=0, the final allocation time is not updated.

As described above, the office-side line concentration device accordingto the present embodiment is configured to, even when a home-side devicehaving a lower upstream rate than the rate of an uplink exists, performaccess control so that an upstream burst signal from the home-sidedevice can be early sent, accumulate a user data frame stream from thehome-side device having a low transfer rate in a FIFO to adjust thetiming of transmission to the uplink, up-convert the user data framestream to that of the uplink speed, and send the resulting user dataframe stream so that user data frames can be seamlessly arranged in theuplink. Therefore, more effective use of bandwidth in the uplink can beachieved.

The embodiments disclosed herein are examples only and are not to beconsidered as restrictive. The scope of the present invention is definedby the Claims rather than by the foregoing description, and all changesthat come within the meaning and range of equivalents to the Claims areintended to be embraced therein.

INDUSTRIAL APPLICABILITY

There are provided an office-side line concentration device, an accesscontrol device, and a computer program therefor capable of effective useof bandwidth in an uplink by the provision of a plurality of receivingmeans connected to each of a plurality of passive optical networks, andan interface means for controlling a transmission timing of user datafrom the plurality of passive optical networks so that user datareceived by the plurality of receiving means can be arranged closely inthe uplink.

1. An office-side line concentration device that accommodates aplurality of passive optical networks, comprising: a plurality ofreceiving means connected to each of the plurality of passive opticalnetworks; and interface means for controlling a transmission timing ofuser data from the plurality of passive optical networks so that userdata received by the plurality of receiving means can be arrangedclosely in an uplink.
 2. The office-side line concentration deviceaccording to claim 1, wherein the interface means controls thetransmission timing so that a difference between a reception timing ofthe user data received by the receiving means and a transmission timingto the uplink can be reduced.
 3. The office-side line concentrationdevice according to claim 2, wherein all upstream transfer rates of userdata in the passive optical networks are identical to an upstreamtransfer rate of the uplink, and the interface means transmits the userdata received by the plurality of receiving means directly to the uplinkwithout accumulating the user data in a buffer.
 4. The office-side lineconcentration device according to claim 3, wherein the interface meanscontrols the reception timing so that a burst signal of a first passiveoptical network and a burst signal of a second passive optical networkare made to overlap and so that an overlapped time can become at least aportion of a time obtained by removing a time corresponding to a userdata frame period and a laser-off period from a burst length of thesecond passive optical network.
 5. The office-side line concentrationdevice according to claim 2, wherein the plurality of passive opticalnetworks include a passive optical network including a home-side devicehaving a lower upstream transfer rate than an upstream transfer rate ofthe uplink, and wherein the interface means controls the receptiontiming so that, when user data from the home-side device having a lowerupstream transfer rate than that of the uplink is up-converted andtransmitted to the uplink, the end of the user data from the home-sidedevice having a lower upstream transfer rate can exist before the end ofthe user data up-converted and transmitted to the uplink.
 6. Theoffice-side line concentration device according to claim 5, wherein theinterface means controls the reception timing so that a burst signal ofa first passive optical network and a burst signal of a second passiveoptical network are made to overlap and so that an overlapped time canbecome at least a portion of a time obtained by removing a time requiredto transmit a user data frame at an uplink speed and a timecorresponding to a laser-off period from a burst length of the secondpassive optical network.
 7. An access control device that controls areception timing of user data from a plurality of passive opticalnetworks, comprising: means for controlling a transmission timing ofuser data from the plurality of passive optical networks so that userdata received by the plurality of passive optical networks can bearranged closely in an uplink; and means for instructing transmission ofa grant including the transmission timing to home-side devices connectedto the passive optical networks.
 8. A computer program for causing acomputer to execute control of a reception timing of user data from aplurality of passive optical networks, the computer program causing thecomputer to execute: a step of controlling a transmission timing of userdata from the plurality of passive optical networks so that user datareceived by the plurality of passive optical networks can be arrangedclosely in an uplink; and a step of instructing transmission of a grantincluding the transmission timing to home-side devices connected to thepassive optical networks.